Examples of known molding systems are (amongst others): (i) the HyPET (trademark) Molding System, (ii) the Quadloc (trademark) Molding System, (iii) the Hylectric (trademark) Molding System, and (iv) the HyMET (trademark) Molding System, all manufactured by Husky Injection-Molding Systems (Location: Canada; www.husky.ca).
FIG. 1A depicts a known valve-gated hot-runner system according to U.S. Patent Application No. 2006/0153945A1 (Inventor: BLAIS et al.; Published: 2006 Jul. 13), which discloses a valve stem that has a reverse taper thereon used in an injection nozzle for a hot runner system. The valve stem is moved downward into a closed position, such that a valve-stem tip plugs or blocks an opening in a gate area, thereby precluding molten plastic from exiting the injection nozzle. The valve stem is moved upward into an open position, thereby allowing molten plastic to flow from the injection nozzle. In the open position, the reverse taper seals a clearance between the valve stem and a manifold bushing, thereby precluding stem leakage or weepage. The reverse taper has a diameter which is larger than an internal diameter of internal passage of the valve bushing or manifold bushing. The valve stem also includes a headless end. According to BLAIS, at page two, paragraph sixteen: “a valve stem is coaxially to and operatively mounted in at least a portion of an internal passage of a nozzle and internal passage of either a valve bushing or a manifold bushing in a hot runner system. The valve stem includes: (i) a shaft movably mounted in the internal passages of the nozzle and either the valve bushing or the manifold bushing, (ii) a first end of the shaft, for plugging an opening in a mold cavity in a first, position, and (iii) a reverse taper on the shaft, for sealing a clearance between the valve stem and either the valve bushing or the manifold bushing in a second position.”
FIG. 1B depicts a known valve-gated hot-runner system according to U.S. Pat. No. 6,840,758 (Inventor: BABIN et al.; Published: 2005 Jan. 11), which discloses a valve bushing assembly for use in an injection-molding apparatus. The injection-molding apparatus includes a manifold block, a valve pin, and an actuator block. The manifold block has at least one melt channel therein. The manifold block has an exterior surface that faces the actuator block, and has a manifold pass-through extending from the exterior surface to the at least one melt channel. The manifold pass-through has a manifold sealing surface therein. The manifold pass-through permits the valve pin to pass therethrough. The actuator block has an actuator attached thereto that is operatively connected to the valve pin. The valve bushing assembly includes a bushing and a spacer. The bushing is adapted to be received in the manifold pass-through. The bushing has a bushing pass-through that is adapted to align with the manifold pass-through and is adapted to slidably receive the valve pin. The bushing has a bushing sealing surface that is adapted to cooperate with the manifold sealing surface to inhibit melt leakage therebetween. The bushing has a bushing shoulder. The spacer is positioned between the manifold block and the actuator block to space the manifold block and the actuator block from each other. The spacer has a first spacer surface that is adapted to contact the actuator block. The spacer has a second spacer surface that is adapted to contact the bushing shoulder. The spacer is adapted to be substantially free of contact with the manifold block. According to BABIN et al. at column five from lines 28 to 36: “The bushing pass-through extends along an axis, and is defined by a bushing pass-through surface. One or more annular grooves may be positioned along the length of the bushing pass-through surface. When the valve pin is positioned in the bushing pass-through, the grooves act as chambers and can be used to collect melt that leaks between bushing and the valve pin. Any melt that seeps into grooves may harden and help to seal against further melt leakage out of manifold melt channel.” According to BABIN et al. at column seven from lines 21 to 27: “Referring to FIG. 2, the spacer may be used to thermally insulate the manifold block from the actuator block. The spacer may also be used to help retain the bushing in place in manifold pass-through and to improve the seal between the bushing sealing surface on bushing and the manifold sealing surface.” According to BABIN et al. at column seven from lines 51 to 59: “The contact area between the second spacer surface and the shoulder may be made relatively small, to reduce the heat transfer between the manifold block and the spacer. Because the shoulder is slightly above the surface of the manifold block, an air gap exists between the second spacer surface and the surface, to further reduce the heat transfer between the manifold block and the spacer.”
FIG. 1C depicts a known valve-gated hot-runner system according to U.S. Pat. No. 5,387,099 (Inventor: GELLERT; Published: 1995 Feb. 07), which discloses a valve gated injection-molding apparatus wherein the reciprocating valve member extends into the melt passage through a sealing bushing. The sealing bushing has a thin steel collar portion which extends forwardly into the melt passage and fits around the valve member to form a seal against leakage of melt rearwardly along the valve member. In the preferred embodiments, the collar portion is thin enough that it is slightly compressed around the valve member by the pressure of the surrounding melt in the melt passage to improve the seal. According to GELLERT at column three from lines 12 to 18: “The elongated valve member extends into the melt passage in the sealing bushing and in order to avoid a problem of the pressurized melt leaking rearwardly along the reciprocating valve member, the sealing bushing has a collar portion which extends forwardly into the melt passage around the valve member.”